DESCRIPTION: (Applicant's Abstract) The RGS family of proteins negatively regulate signaling through Gi/o G-alpha subunits. The RGS9 subtype is (i) predominantly expressed in brain regions implicated in cocaine's behavioral effects and (ii) is markedly down regulated following chronic cocaine. These two features make RGS9 a good candidate to mediate some of the changes in neural transmission that subserve cocaine addiction. Nevertheless, prior to the discussion of RGS9 as a potential drug target, the relevance of RGS9 down regulation to cocaine's addictive qualities must be further established. To determine if cocaine-induced alterations in RGS9 levels parallel changes in signal transduction thought to be critical to dependence, temporal and spatial characteristics of RGS9 regulation will be determined using Northern/Western blot and in situ hybridization analyses. The RGS subtype specificity of cocaine-induced changes will also be evaluated. The requirement of dopamine receptors for cocaine effects on RGS9 levels will be assessed using specific agonists/antagonists and transporter blockers. Finally, to more directly assess the role of RGS9 in drug addiction, we will begin work to create a line of inducible RGS9 knockout mice. This will build on early cloning experience I have already received in the laboratory. Together, these integrated, multidisciplinary studies will advance my training as well as elucidate the role of RGS proteins as novel mediators of cocaine addiction.